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Abstract Background and Objective: Efficient human resource is the major advantage of an organization over others. Commitment to organization not only may reduce sick leave, delays and displacements but also give rise to a significant increase in productivity, more vitality among staff, better attainment of the organizations' goals and personal aims. This study aimed to evaluate the relationship between personal characteristics and organizational commitment among medical laboratory staff. Material and Methods: This correlational study was conducted on 105 medical laboratory staff selected randomly in Gorgan, 2010-2011. The instruments for data collection were NEO personality inventory and Meyer and Allen's model of organizational commitment. Results: The relationship between organizational commitment and the variables such as neuroticism, openness, agreeableness and Conscientiousness was positively significant but that was not the case for extroversion characteristic. Conclusion: Given the positive relationship between personality characteristics and organizational commitment, we recommend improving these characteristics to enhance staff commitment to organization. Keywords: Organizational Commitment, Personality Characteristics, Laboratory Staff